1. Field
The present disclosure relates generally to the formation of composite structures. More particularly, the present disclosure relates to composite sandwich structures. Yet more particularly, the present disclosure relates to a method and apparatus for forming a sandwich structure comprising a thermoplastic material.
2. Background
Composite materials may be tough, light-weight materials created by combining two or more functional components. For example, a composite material may include reinforcing fibers bound in a polymer resin matrix. Resins used in composite materials may include thermoplastic or thermoset resins. A thermoplastic material may become soft upon heating and may harden upon cooling. A thermoplastic material may be able to be repeatedly heated and cooled. A thermoset material may become hard when heated. The fibers may be unidirectional or may take the form of a woven cloth or fabric.
Composite structures that include a core sandwiched between face sheets are used for many purposes. This arrangement forms a sandwich structure. Often the core includes cells or cavities. These cells or cavities are employed to reduce the weight of the composite structure as compared to a similar structure made from solid materials. Solid materials are materials without cells. The reduced weight of these composite structures has led the aircraft industry to use such composite structures to reduce the weight of aircraft components.
The time to create a sandwich structure from thermoset materials may be undesirable. For example, thermoset materials may be laid up by hand or by machine to form the shape of the sandwich structure. The speed of laying down composite material may be limited. Further, curing a thermoset material may require several hours. In addition to holding the thermoset material at a curing temperature for several hours, conventional autoclaves using resistive heating to cure thermoset materials may further require several hours for heating up and cooling down.
Consolidating a thermoplastic material may take less time than curing thermoset material. However, the time for resistive heating during consolidation of thermoplastic material may still be undesirable.
Currently, thermoplastic sandwich structures may be produced using fasteners. The use of fasteners increases the weight of the thermoplastic sandwich structures. The use of fasteners may also increase the time to create thermoplastic sandwich structures.
Accordingly there is a need for a method and assembly for producing a thermoplastic sandwich structure without the use of fasteners. There is also a need for a method of consolidating thermoplastic sandwich structures. Further, there is a need to consolidate the thermoplastic sandwich structures faster than using resistive heating to reduce at least one of cost of producing thermoplastic sandwich structures and the amount of time to produce thermoplastic sandwich structures.
Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as other possible issues.